Dye sublimation inks have long been used for printing on polyester-based materials and objects. Conventionally, sublimation printing processes have used thermal printers and dye transfer paper and have employed analog printing methods. The dye sublimation inks include a pigment suspended in a liquid solvent, such as water. Inkjet inks and inkjet printers have also recently been used for sublimation printing processes.
The market for digital textile printing has grown substantially in recent years. This has led to increased usage of and interest in solvent-based, e.g. water-based, dye sublimation inks. Outside of textile applications, other polyester-based materials are also decorated using dye sublimation technology. Examples include films, containers, packaging, and materials having a polyester coating, such as wood or metal.
Two types of printing processes can be used in sublimation printing. Direct printing requires that ink is jetted directly onto a substrate, cured, and then thermally treated such that the dye diffuses from the ink into the substrate. Indirect printing requires that ink is printed onto heat-resistant transfer paper or another transfer material and cured, e.g. via UV radiation. The transfer paper is placed over a substrate and heat is applied that causes the dye to transfer to the substrate from the transfer paper and form an image.
Indirect printing is both more costly and more complex due to the presence of the transfer paper. Moreover, the transferring process can be materially hindered if the image is not printed onto a flat substrate.
Conventionally, both direct and indirect printing have been carried out only on flat substrates. Because print quality of direct printing relies on accuracy of ink drop placement, the distance between the printer head and the substrate is critical. The distance, which is generally a few millimeters or less, must be kept constant or nearly constant to limit the effects of velocity variability, airflow, etc., on drop placement. Similar issues plague indirect printing. It is often difficult, if not impossible, to conform transfer paper to complex shapes.